Heat and pressure 60 miles down pushed up molten rock inside a volcano that had last erupted in the year 1595, melting ice and snow at the top of 17,716-foot Nevado del Ruiz -- snow peak of Ruiz -- and sending a thundering locomotive of hot mud, water and rock down a descent of some 15,000 vertical feet to crash upon the towns and farms in the valleys below. Thousands were buried and broken late Wednesday by this immense assault from the Andes in the coffee- growing part of Colombia 85 miles from Bogot,a. It goes on the lists of the great megadeath catastrophes. Colombia, already battered by many man- made woes, did not need this natural one.

Almost invariably when these things happen it turns out that there were rumblings and other warning signs, but they were imprecise in their implications and there was only an uncertain possibility of heeding them. A countryside that has not been touched by the fury in four centuries cannot reasonably be expected to go on alert for an emergency that experts had begun to plan for but had not been able to pin down in time. The mud slides that had been thought possible were expected to move at a rate permitting convenient evacuation; when the mud came it seems to have been moving -- think of it -- at the fantastic speed of 20 to 30 miles per hour.

Evidently there are 20 or more other peaks in the Andean chain with a like potential for what the experts call "renewed activity." The Mexican earthquakes of September and even the eruption at Mount St. Helens in Washington state in 1980 arose from similar causes. The science of "volcanology" would seem to deserve more urgent attention than it has so far received.

The brunt of the horror is necessarily suffered and absorbed by the place where it happens. The sharing of grief and the providing of aid, however, are the essential means by which comradeship and fellow feeling are registered in these terrible moments. What outsiders offer cannot be much more than a token, but it is a vital token. The compassion of Washington residents will surely be stirred by the awareness that Colombia, which has far fewer resources with which to cope, has experienced a tragedy of a scope hundreds -- thousands? -- of times worse than what the flooding produced in this region a week or so ago.